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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
341

Advanced studies of membrane fouling : investigation of cake fouling using fluid dynamic gauging

Lewis, William J. T. January 2015 (has links)
Membrane filtrations are widely used in process industries but are almost always limited by fouling, a highly studied and significant problem. This is defined as unwanted material deposited on a membrane surface or within its pores, which can significantly impair performance and/or reduce operating life. The strategies to mitigate fouling include cleaning in place, modified membranes, and optimisation of operating conditions. In order to correctly select or target improvements to any such measures a detailed mechanistic understanding of the fouling process is important, which requires more than just performance data from unit operations. One key mechanism is that of cake fouling, which describes the build-up of particle layers on the surface of the membrane. Its growth and physical properties are difficult to assess. In this project the technique of fluid dynamic gauging (FDG) has been explored as a means to study cake fouling. This simple, yet robust method allows for estimation of thickness and strength of cake fouling at high concentrations and opacity, without any prerequisite knowledge of feed properties. Studies described herein focused on microfiltrations through cellulosic membranes. FDG was used to track cake growth during filtrations of polydisperse yeast suspensions (which contained large agglomerates), demonstrating its capability to work with non-ideal, food-like substances. Later studies used more predictable suspensions of hollow glass spheres, which were used to assess various filtration models. The most effective was found to be an interpretation of the critical flux laws, which were used to successfully identify pore fouling during filtrations of Kraft lignin, an observation supported by FDG measurements. Another novel achievement of this project was the development of an automated apparatus for performing FDG in cross-flow membrane filtration. This allowed for much faster acquisition of results, and demonstrated the potential for its development into an autonomous system capable of making thickness measurements on the fly during filtrations. The most reliable protocol for determining cake growth rates was by repeated filtrations in which destructive thickness testing was performed at selected time points. This was because continuous or even repeated thickness measurements during a single filtration were found to cause too much disturbance to the fouling layer. Computational fluid dynamics was used to simulate shear stress profiles on the fouling layer, while also providing a more accurate means to calibrate the automated apparatus. Erosion caused by FDG readings, when viewed under a microscope, was found to conform to the shear stress profiles predicted by simulations.
342

Dynamic phase transitions in biased ensembles of particle systems with repulsive interactions

Thompson, Ian January 2015 (has links)
We study dynamic phase transitions in the constant-volume and constant- pressure ensembles of two different systems: a one-dimensional system of diffusive hard particles and a three-dimensional glass-former of nearly-hard repulsive particles. The dynamic transitions are observed using ensembles of trajectories biased with respect to their dynamic activity, biasing to greater or lower activities than equilibrium allows us to sample different dynamic phases. We perform finite-size scaling of the transitions with respect to sys- tem size and observation time, and compare them to first-order phase tran- sitions. The two ensembles are not equivalent in the one-dimensional model. We compare our results to analytic predictions for diffusive systems in both the active and inactive phases, there are structural signatures for both dy- namic regimes. The active phases show hyperuniform ordering and the inac- tive regimes show jamming behaviour, local jamming in the constant-volume ensemble is achieved through phase separation. In the three-dimensional sys- tem we observe a dynamic transition to a glassy inactive phase, there is no obvious structural change and the structural relaxation time increases sig- nificantly. We take configurations from the active and inactive phases and subject them to a jamming protocol in order to compare the final density of the jammed packings. Previous work shows that the inactive phase of glass-forming systems have a different distribution of vibrational modes and a higher compressibility, this suggests that the jamming behaviour should differ between the two phases. We show that jammed packings generated from inactive configurations are denser than those generated from active configurations.
343

Exploring the benefits and implications of dynamic partial reconfiguration using Field Programmable Gate Array-System on Chip architectures

Beasley, Alexander January 2019 (has links)
Demands on modern computing are becoming more intensive. Keeping up with these demands has increasing complexity. Moore's Law is in decline. Increasing the number of cores on a device has diminishing returns. Specialised architectures provide more efficient and higher performing processors. However, it is not always practical to include every architecture on every device. Running non-native tasks on architectures often results in a drop in performance. This research examines the benefits and limitations of Field Programmable Gate Arrays - Systems on Chip (FPGA-SoC) devices to provide flexible hardware accelerators for heterogeneous architectures. A number of topics are covered, including hardware acceleration of floating-point mathematical functions, dynamic reconfiguration and high-level synthesis. A number of case studies are presented. Dynamic reconfiguration is used to change the configuration of the FPGA at runtime, allowing the hardware accelerators to be changed depending on the current processor tasks. Changing accelerators at runtime has limitations, such as data perturbation. Context switching techniques are applied to the hardware to prevent loss of data and enable de-fragmentation of the FPGA. High level synthesis techniques are used in conjunction with the presented hardware accelerators to synthesise high-level languages into hardware descriptions with optimisations. Techniques for runtime synthesis of hardware accelerators are presented. These can be combined with dynamic reconfiguration to configure FPGAs with appropriate hardware accelerators from a high-level language at runtime. The research demonstrates that FPGA-SoC devices have the potential for providing reconfigurable accelerators for processors in heterogeneous architectures. Metrics show that the FPGA configurations can perform better than other commercial processors. It was demonstrated that it is possible to context switch hardware at runtime, meaning the most can be made of the FPGA-SoC at all times, even as situations change. However, there are many limitations that still need to be overcome, such as management of the implemented hardware, synthesis of new hardware at runtime, reconfiguration times, interfacing of hardware with software and the design of hardware accelerators.
344

Reflection and Transmission of a Plane Electromagnetic Wave on a Moving Boundary Between Two Dielectrics

Teixeira, Elizabeth 03 May 2006 (has links)
This work introduces formulae of Fresnel type related to reflection and transmission of a plane electromagnetic wave from a moving boundary separating two isotropic dielectrics. The dielectrics themselves remain immovable, so, the ensuing material formation represents an example of an activated dynamic material assembled from the LC-arrays serving as the discrete versions of each dielectric.
345

Design Evaluation of a Duplex Circular Wet Well Pumping Station Under Steady State and Dynamic Operating Conditions

Mailloux, James Thomas 29 April 2010 (has links)
Duplex Circular Wet Well (DCWW) lifting pump stations are utilized for pumping clear and solid-bearing liquid. Understanding the effect of design criteria on pump performance is important to minimize maintenance costs and maximize efficiency. There are currently no known full-scale laboratory studies that have been performed to investigate the overall design of DCWWs. The objective of the research was to evaluate the impact of various design criteria, such as internal geometry and operating conditions on the performance of DCWW pump stations and provide documentation and recommendations which will be used to augment the current Hydraulic Institute/American National Standard for Pump Intake Design (ANSI/HI 9.8-1998), (HI) guidelines. The research was conducted in two phases; Phase 1 consisted of performing a comparative analysis of the basic flow patterns within the wet well by means of Computational Fluid Dynamics (CFD), Phase 2 consisted of performing detailed evaluations of various design aspects on pump performance using a full-scale Physical Model constructed for the research. The CFD research provided indications regarding potential performance problems that may occur due to poor flow patterns and potential pump suction swirl, while the physical research provided a basis for determining the relative advantages of different designs. The physical research included the evaluation of general flow patterns, free-surface and subsurface vortices, air entrainment and pump suction swirl. Measurement of the steady state swirl within the pump showed unacceptable performance in accordance with the HI acceptance criteria. Swirl data collected under real-world dynamic operating conditions showed that the pump typically did not experience the adverse conditions indicated at steady state. Normal (symmetrical) pump orientation resulted in more favorable operation in terms of pump swirl and ingestion of entrained air than a coplanar (inline) condition. A minimum water elevation was established to minimize air-entrainment and swirl entering the pumps, reducing possible effects such as cavitation and vibration of the pump impeller. Air-core subsurface vortices were present under the pumps, requiring pump-cones to be installed. The collection of real-time dynamic data will allow design engineers to better understand actual pump performance under normal cycling and clean-out modes, reducing the operating time under unfavorable conditions and overall maintenance requirements.
346

Design and Analysis of a Rapid Kinetic Energy Transmission Mechanism

Benson, Brian C 26 April 2011 (has links)
The rapid release of energy in mechanisms is often limited by conversion of potential energy to kinetic energy. The use of a flywheel to store energy over time eliminates this constraint. Using this principle, a lightweight and compact energy transmission mechanism has been developed for robotic combat applications. The purpose of the proposed design is to throw an opposing robot ten or more feet into the air. This design incorporates a flywheel, a self-resetting dog clutch with built in shock absorbing rubber for impact mitigation, and an optimized four-bar linkage to deliver the energy. A mathematical model of the dynamic system has been developed to analyze and aid in the design process. Testing of subsystems was performed to validate the design. A final design is proposed with the recommendation that it be built and tested. A validated design is applicable to many real-world problems that require rapid kinetic energy release including reconnaissance robots required to hop high fences.
347

Textilen

JA HAN, JEANNINE January 2011 (has links)
II. ABSTRACTTextilen is a project designed to draw the human senses to the world of microand macro patterns in sound and color and to explore methods for correlating thetwo mediums. This goal is accomplished via a two-fold process. First of all, patternsin sound are explored through the use of textile materials by way of creating newinstrument interfaces, synthesizer sources, and tones in music harmony. Secondly,the patterns of the textiles themselves are explored and incorporated into costumesand characters so an association between the emanating sounds and the visualstimulus presented by the characters, highlights the underlying patterns used inboth mediums. The final presentation will be organized in the context ofperformance art in a controlled sound environment.A subsidiary aim of the project has been to develop myself as an artist and bringmy interests and inspirations into an artistic context. In order to execute this,a design method that incorporates practical and theoretical research alongsidetechnical invention, graphic design, sound experimentation, and characterdesign was chosen. / Program: Master in Textile Design
348

A chuva no Distrito Federal : o regime e as excepcionalidades do ritmo /

Barros, Juliana Ramalho. January 2003 (has links)
Orientador: João Afonso Zavattini / Banca: Marcos Norberto Boin / Banca: José Bueno Conti / Resumo: Por fazer parte de uma região cuja dinâmica climática ainda é pouco conhecida, objetivou-se, ao estudar o Distrito Federal, oferecer uma contribuição para a caracterização do quadro climático local. Para isto, foi feita uma breve caracterização do quadro climático regional no qual esta área encontra-se inserida para, então, chegar-se à caracterização de seu regime pluviométrico. Tendo em vista que nas regiões tropicais as variações pluviais traduzem o ritmo atmosférico, a partir da caracterização do regime das chuvas no Distrito Federal, foram analisados, sob o ponto de vista da climatologia dinâmica, episódios pluviais de caráter habitual e excepcional. Os resultados climatológicos obtidos permitiram que se chegasse à compreensão do regime pluvial, bem como do ritmo de sucessão de alguns estados atmosféricos que ocorrem na área em questão. Espera-se, assim, que este trabalho represente um estudo de base que possa servir de subsídio a futuras pesquisas de climatologia sobre a área em questão. / Abstract: Being part of an area in wich the climatic dynamics still isn't well know the study of Distrito Federal aims a contribution to the characterization of the local climatic configuration. For that, a small characterization of the regional configuration was done, in wich this area is inserted, reaching then a characterization of the pluviometrical regime. Knowing that in the tropical areas the pluvial variations state the atmospherical rithm, based in the characterization of the rain's regime in the Distrito Federal, under the dynamical climatology's point of view, pluvial episodes of habitual and exceptional nature were analysed. The climatologic results allowed to comprehend the pluviometrical regime, as well as the succession's rithm of several atmospherical states, which occur in the studied area. Hope is that work represents a study which serves as a sudsidy for future climatological researches of this area. / Mestre
349

Exploring educational psychologists' use of using dynamic assessment in the Early Years Foundation Stage

Hussain, Sobia January 2017 (has links)
Dynamic assessment represents an opportunity for educational psychologists to utilise a play-based approach for assessing the functional behaviour of children who struggle to perform in formal testing situations (Tzuriel, 2000; Hill, 2015). A systematic literature review aims to evaluate available empirical research on the use of dynamic assessment approaches within the early years to provide a clearer view of the evidence for their use and to support educational psychologists' development of such approaches within their professional practice. The review of this evidence indicated mixed results for the usefulness of dynamic assessment in the early years phase and warranted closer inspection of the use of dynamic assessment by educational psychologists. In the empirical project, a purposive convenience sample was used. Two practising educational psychologists were interviewed using semi structured interview schedules and observed delivering dynamic assessment in the Early Years Foundation Stage. Interviews were analysed using thematic analysis and a content analysis was used to analyse the videoed observations. The findings of this empirical project highlight the type and level of mediation required for dynamic assessment of children in the Early Years Foundation Stage; how educational psychologists evaluate the usefulness of dynamic assessment for assessing and identifying the needs of children in the Early Years Foundation Stage; and the implications of dynamic assessment for intervention for children in the Early Years Foundation Stage. Implications are discussed for promoting the use of dynamic assessment among educational psychologists as a useful tool for assessment of children in the early years age phase.
350

Dynamic optimization of classification systems for adaptive incremental learning.

Kapp, Marcelo Nepomoceno 25 May 2016 (has links) (PDF)
Tese de Doutorado, defendida na Université Du Québec, Canadian. 2010 / Submitted by Nilson Junior (nilson.junior@unila.edu.br) on 2016-05-25T23:32:09Z No. of bitstreams: 2 MKapp_PhD_2010.pdf: 2076219 bytes, checksum: db47dfe0b9ee92594b31d05a2f2e7fef (MD5) Recibo Deposito Legal_TESE_Marcelo Nepomoceno Kapp01.pdf: 205561 bytes, checksum: ac4617abe7f6d68472c1ac6ac02abd26 (MD5) / Made available in DSpace on 2016-05-25T23:32:22Z (GMT). No. of bitstreams: 2 MKapp_PhD_2010.pdf: 2076219 bytes, checksum: db47dfe0b9ee92594b31d05a2f2e7fef (MD5) Recibo Deposito Legal_TESE_Marcelo Nepomoceno Kapp01.pdf: 205561 bytes, checksum: ac4617abe7f6d68472c1ac6ac02abd26 (MD5) Previous issue date: 2010 / An incremental learning system updates itself in response to incoming data without reexamining all the old data. Since classification systems capable of incrementally storing, filtering, and classifying data are economical, in terms of both space and time, which makes them immensely useful for industrial, military, and commercial purposes, interest in designing them is growing. However, the challenge with incremental learning is that classification tasks can no longer be seen as unvarying, since they can actually change with the evolution of the data. These changes in turn cause dynamic changes to occur in the classification system’s parameters If such variations are neglected, the overall performance of these systems will be compromised in the future. In this thesis, on the development of a system capable of incrementally accommodating new data and dynamically tracking new optimum system parameters for self-adaptation, we first address the optimum selection of classifiers over time. We propose a framework which combines the power of Swarm Intelligence Theory and the conventional grid-search method to progressively identify potential solutions for gradually updating training datasets. The key here is to consider the adjustment of classifier parameters as a dynamic optimization problem that depends on the data available. Specifically, it has been shown that, if the intention is to build efficient Support Vector Machine (SVM) classifiers from sources that provide data gradually and serially, then the best way to do this is to consider model selection as a dynamic process which can evolve and change over time. This means that a number of solutions are required, depending on the knowledge available about the problem and uncertainties in the data. We also investigate measures for evaluating and selecting classifier ensembles composed of SVM classifiers. The measures employed are based on two different theories (diversity and margin) commonly used to understand the success of ensembles. This study has given us valuable insights and helped us to establish confidence-based measures as a tool for the selection of classifier ensembles. The main contribution of this thesis is a dynamic optimization approach that performs incremental learning in an adaptive fashion by tracking, evolving, and combining optimum hypotheses over time. The approach incorporates various theories, such as dynamic Particle Swarm Optimization, incremental Support Vector Machine classifiers, change detection, and dynamic ensemble selection based on classifier confidence levels. Experiments carried out on synthetic and real-world databases demonstrate that the proposed approach outperforms the classification methods often used in incremental learning scenarios.

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